Corneal endothelium of higher animals plays irreplaceable roles in maintaining corneal transparency and thickness and supplying nutrition for cornea. If cornea is infected or injured by surgery etc., the number of corneal endothelial cells will decrease in varying degrees. Once the density of corneal endothelial cells is lower than the critical density required for maintaining the physiological function of corneal endothelium, irreversible pathological alteration will occur in corneal endothelium, which eventually results in primary corneal endotheliopathy. At present, there are at least 800,000 patients suffering from primary corneal endotheliopathy in China. Although these patients can be cured by cornea transplantation, most suffers are not able to restore their sight ascribed to a severe lack of corneal donor. In recent years, development of corneal tissue engineering brings new hope for in vitro reconstruction of tissue-engineered human corneal endothelium and primary corneal endotheliopathy therapy. How to reconstruct a tissue-engineered human corneal endothelium in vitro using human corneal endothelial cells and appropriate scaffold carriers has already become an academic hotspot. Research on in vitro reconstruction of human corneal endothelium is firstly launched since 1992. After that, Griffith et al. (1999) successfully reconstructed functioning human corneal equivalents possessing roughly similar morphological features, transparency and tissue structure as normal cornea by employing oncogene-transfected immortalized human corneal epithelial cells, human corneal stroma cells, human corneal endothelial cells and glutaraldehyde cross-linked collagen. They paved a way for in vitro reconstruction of human corneal endothelium. However, the utilization of oncogene-transfected and carcinogenic potential possessed immortalized keratocytes heavily restricts these cells in human corneal endothelium reconstruction for therapeutic purpose. Ishino and Mimura (2004) reconstructed human corneal endothelium cell sheets performing similar functions to normal corneal endothelium by using human corneal endothelial cells cultured in vitro to the 4-5th passage and denuded human amniotic membrane and collagen sheets, respectively. Lai (2007) produced a functionally similar corneal endothelium cell sheet to human corneal endothelium by using primarily cultured human corneal endothelial cells adopted from an adult human cornea preserved in eye bank and a modified scaffold carrier, N-(1-methylethyl)-2-propenamid homopolymer. Hitani (2008) from Medical School, the University of Tokyo, obtained human corneal endothelial cell sheets with analogical function of normal human corneal endothelium by culturing human corneal endothelial cells on a cell culture insert. These achievements paved a way of the reconstruction of tissue-engineered human corneal endothelium using non-transfected HCE cells. Nevertheless, seeder cells employed in above methods were either primarily cultured or 4-5th passage subcultured human corneal endothelial cells in 24-well culture plates from corneas preserved in eye bank. The limited number of seeder cells restricted in vitro reconstruction of tissue-engineered human corneal endothelium, consequently, reconstructed corneal endothelium equivalents for clinical cornea transplantation are not sufficient. These methods can be merely used in experimental research. They can not meet the great demand of clinical therapy for patients suffering from primary corneal endotheliopathy (over 0.8 million in China and over 10 million globally).
In 2005, Fan et al. successfully established a non-transfected human corneal endothelial cell line without any tumorigenic potential for the first time all over the world. Hereto the problem in source of seeder cells for large-scale reconstruction of tissue-engineered human corneal endothelium is figured out. Hence it is now a major goal for worldwide ophthalmologists to establish a manufacturing technology of ideal scaffold carriers as soon as possible, and then to find a reconstruction method of tissue-engineered human corneal endothelium using non-transfected human corneal endothelial cells and ideal scaffold carriers. This is also the key for clinical application of tissue-engineered corneal endothelium and the key to benefit the patients suffering from primary corneal endotheliopathy all over the world.